The present invention relates to an apparatus for adjusting the height of a strut for supporting a member at a predetermined height and more particularly to improvements in a strut height adjusting apparatus designed to automatically adjust the height thereof in proportion to a difference in level on the side of the strut height adjusting apparatus according to a signal transmitted to indicate a reference level and also capable of measuring the difference in height at a plurality of measuring points.
With the development of office automation (OA) equipment, an increasing number of various electronic equipment have come to be used in business offices. This has resulted in necessitating cable connectors for connecting socket plugs as inlets for several different power supplies and electronic equipment. Today, it is common to construct double-bottomed office floors with connection codes wired therein so that socket plugs and cable connectors may be exposed on the floors close to the installed equipment.
Such a double-bottomed office floor is constructed by covering the floor with a plurality of floor panels at fixed height on a base. The panels are typically square with each side being 30 to 50 cm in length and 15.about.50 mm thick. The panels are composed of a panel base material made of glass fiber reinforced concrete called GRC, calcium silicate or the like, a steel plate as a liner added to the underside of the panel base material and a carpet tile or a tile of vinyl chloride as a surface plate. Each floor panel is reinforced by a strut for supporting a panel's corner together with the corner of another adjoining floor panel at a fixed height. The outer periphery of the strut is threaded and a support member such as a nut whose central portion meshes with the threads is prepared. The height of the floor panel is adjusted by turning the support member. After all the support members are positioned at the same level, a pedestal is fitted to the strut in such a way that its lower end abuts against the support member and the corner of the floor panel together with the corner of another floor panel adjacent thereto is mounted on the pedestal to cover the floor with the floor panels at the desired uniform level.
Another method of constructing a double-bottomed floor comprises the steps of forming a notch in each corner of a floor panel, the notch being large enough for at least a quarter of a strut to be received thereby, securing a nut to locate a threaded hole at the notch beforehand, fitting the strut in the nut and installing the combination of them on a base material, arranging a floor panel without such a nut next to what has the nut for common use in supporting the floor panel without the nut, and adjusting the height of the nut by turning the strut. This method of construction is advantageous in that even after the floor has completely been covered with the floor panels, level adjustments can be made by inserting a jig such as a screwdriver through the notches in the corners of the floor panels and turning the struts. The maximum diameter of the strut is about 10 mm. Decorative surface materials such as a carpet or glazed vinyl chloride tiles can be spread on the floor panels for covering, the openings for the struts.
A practice common with the aforementioned two methods of laying floor panels is to ink meshes (normally 450 to 500 mm meshes) for matching the size of the floor panel on the base material in order to install struts at the intersection points of the ink lines. This practice is employed to make uniform the height of all struts, that is to place, support members on the same plane.
Conventional methods of covering a floor with floor panels includes, in order to make the height of all struts uniform on the same plane, providing a reference strut for every 10 to 20 struts, and adjusting the height of these struts using a measuring level and a graduated rod called a staff to adjust the support members of the remaining struts existing between the reference struts to the same height of the reference strut by stretching a snapping line between the support members of such reference struts. Under the conventional methods, however, at least two skilled persons are required to make height adjustments using the levels and the staffs. Further, the technicians must continuously bend down during the work resulting in frequent backaches.
In the field of construction, on the other hand, Spectra Physics Company of the United States markets an automatic level control apparatus under the trade names of "Electronic Level EL-1" (hereinafter called "EL-1") and "Level Eye 1077" (hereinafter called "Level Eye"). The apparatus is equipped with a laser emission unit for emitting a laser beam at a desired preset level and designed, upon receiving the laser beam from the laser emission unit, to produce a signal which varies with the vertical movement of the position of the beam received for displaying a difference in level. More specifically, EL-1 is first secured to a tripod and set to a desired level, whereas Level Eye is fitted to a member whose height is to be adjusted. By varying the level of the member until Level Eye receives a laser beam from EL-1 in the optimum condition, the member can be set to the desired level. Moreover, it is unnecessary to move EL-1 once it has been set even though there are places where the level has to be measured as the laser beam from EL-1 is rotatably emitted in the horizontal direction. Since only Eye Level needs to be moved, one worker can perform the whole operation.
Japanese Patent Laid-Open No. 213559/1990 illustrates a strut height adjusting apparatus which is capable of making struts installed on a base material automatically uniform in height while utilizing the previously noted automatic level control and of being operated by one person without bending. Referring to FIG. 5, the strut height adjusting apparatus, includes a laser beam emitter 3 fitted onto, for instance, a tripod 2 on a base material 1 and used for rotatably emitting a laser beam in the horizontal direction at a reference level (or hypothetical level) and a strut height adjusting unit 4 which functions to make the struts uniform in height upon receiving the laser beam emitted from the laser beam emitter 3. The term "hypothetical level" refers to a hypothetical reference plane established above a base plane among a central light source and a plurality of strut height adjusting apparatus, in which the hypothetical level reflects the desired position for the secondary floor. The strut height adjusting unit 4 further includes a rotary unit 8 for rotating a laser beam receiving unit 5 and a nut 7 on a bolt strut 6 for a floor panel, a motor 9 for driving the rotary unit 8, a control unit 10 for controlling the rotation of the motor 9 on receiving a signal from the laser beam receiving unit 5, a handle 11 for holding upright the strut height adjusting unit 4 and a level 12 as a guide for holding upright the strut height adjusting unit 4. The laser beam receiving unit 5 is formed with a plurality of semiconductor light receiving elements arranged longitudinally as position detecting elements 5a. The laser beam receiving unit 5 generates a match signal when a position detecting element 5a located in the center of the laser beam receiving unit 5 receives the laser beam. The control unit 10 causes a signal tone to occur as the received laser approaches a predetermined level. Alternatively, a bar mark can to be displayed on a display unit to indicate differences in height. The term "bar mark" refers to a visual display indicating whether the laser beam directed to a selected one of the strut adjusting apparatus is above or below the desired hypothetical plane. This term is well known in the art as indicative of a particular type of display mechanism. The control unit 10 processes the signal from the position detecting element 5a so as to convert it into position data for controlling the rotation of the motor 9 clockwise and counterclockwise according to the position data.
With this arrangement, the laser beam emitter 3 is placed at any given position on the base material 1 to set the hypothetical level by means of the laser beam, and the strut height adjusting unit 4 is set upright by fitting the rotary unit 8 of the strut height adjusting unit 4 into the nut 7 of the bolt strut 6 while holding the handle 11 with the hands and also watching the level 12. When the position detecting element 5a of the laser beam receiving unit 5 receives the laser beam, the control unit 10 identifies which one of the position detecting elements has received the laser beam and rotates the motor 9 clockwise or counterclockwise according to the data on the difference in height between the hypothetical and actual levels. When the motor 9 rotates clockwise, the nut 7 ascends along the bolt strut 6 and when it rotates counterclockwise, the nut 7 descends. Since the rotation of the motor 9 results in moving the strut height adjusting unit 4 up and down as the nut 7 moves up and down, the control unit 10 stops the motor 9 when it has sensed that the position detecting element 5a in the center of the laser beam receiving unit 5 has received the laser beam. When the motor 9 stops rotating the nut 7 is then anchored at the fixed position of the bolt strut 6. This process is applied to all bolt struts 6 so that all the nuts 7 can be positioned on the same plane.
The aforementioned strut height adjusting apparatus is useful for arranging the positions of respective strut height adjusting members along one preset hypothetical level. Although the setting of the hypothetical level is normally based on the height of the floor at the doorway, the height of the floor tends to vary with respect to the doorway height when a double-bottomed floor is constructed in a room having more than one doorway. This makes it necessary to measure the height of the floor at each doorway to obtain the mean value, for example, for the purpose of setting a hypothetical level. As a consequence, measuring levels, staffs and the like must be employed individually to measure the height of the desired level.
Although the aforementioned level of strut height adjusting unit is designed to operate in a perpendicular position in accordance with the position of bubbles in the hermetically sealed water. Such a level is too sensitive in that slight jolting allows the bubble to move and if much attention is directed to the level, the fitting of the strut height adjusting unit to the strut may be neglected, thus decreasing work efficiently.